sedimentary
Chert / River Stone
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Grey, black, tan, and brown; Luster: Waxy to dull; Texture: Microcrystalline with a conchoidal fracture pattern; Specific Gravity: 2.65.
- Hardness
- 6
- Color
- Grey, black, tan, and brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Grey, black, tan, and brown; Luster: Waxy to dull; Texture: Microcrystalline with a conchoidal fracture pattern; Specific Gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. This specific specimen has been rounded and smoothed by water transport in a river or coastal setting.
Uses & applications
Historically used for stone tools (arrowheads/scrapers) due to its sharp fracture edges. Today it is used in construction aggregate and as decorative landscaping gravel.
Geological facts
Chert was one of the most important materials for early humans because its conchoidal fracture allows it to be knapped into extremely sharp edges. It is sometimes called flint when found in chalk or limestone deposits.
Field identification & locations
Identify in the field by its hardness (will scratch glass), waxy luster on fresh surfaces, and smooth, rounded water-worn shape. Commonly found in riverbeds and glacial deposits.
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